This application is based on, and claims the benefit of priority of, prior Japanese Patent Application No. 2001-132571 filed on Apr. 27, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an injection-amount measuring unit for measuring a fuel-injection amount of a fuel injector.
2. Description of Related Art
An injection-amount measuring device shown in FIG. 3 is a main part of an injection-amount measuring unit 110 for measuring an injection amount of an injector 100. A test fluid is supplied to the injector 100 from a pump (not shown) and the like through a fluid supply passage 115. A noncombustible fluid, substantially having the same viscosity as fuel, is used as the test fluid to prevent the test fluid from catching on fire, burning, and the like.
The injector 100 injects the test fluid from an injection hole 104 by detaching a needle 102 from a valve seat. That is, the needle 102 breaks contact with the valve seat 103. The needle 102 detaches from the valve seat 103 against an applied force of a spring 106 by energizing a coil 105. The spring 106 applies the force to the needle 102 in a direction where the needle 102 is seated on the valve seat 103 that is, in a direction causing the injection hole to close. The applied force of the spring 106 is adjusted using a feed distance of an adjusting pipe 107. The adjusting pipe 107 is guided by and enclosed within a housing 101.
The force of the spring 112 is applied to a valve member 111 of the injection-amount measuring device in a downward direction in FIG. 3. The valve member 111 is moved upward in FIG. 3 by attaching the injector 100 to the injection-amount measuring device 110 so that a fluid passage 116 provided in the valve member 111 communicates with the fluid supply passage 115. A flow meter 120 measures an amount of the test fluid flowing in the fluid supply passage 115 that is, an injection amount of the injector 100. A pressure gage 121 measures a pressure of the test fluid flowing in the fluid supply passage 115.
The needle 102 is made to reciprocate by supplying a pulse current shown in FIG. 4 to the coil 105. When the needle 102 is repeatedly seated on and detached from the valve seat 103 using an ON current and an OFF current of the pulse current, transmitted waves and reflected waves are generated 100 in the fluid within the injector. Then, as shown in FIG. 4, pressure pulsation is generated in the fluid within the injector. When the pressure pulsation is generated in the test fluid, the measured injection amount may fluctuate for every injection of the injector. The injection amount of injector can be accurately measured by increasing the number of injections and calculating an average injection amount. However, it takes a relatively long time to measure the injection amount in this manner.
A frequency of the pressure pulsation, a pressure wave shape and a pressure wave amplitude thereof are changed by a length, arrangement structure, and the like of piping for supplying the test fluid to the injector. Here, plural injection-amount measuring units are set, and a length, arrangement structure, and the like of piping for supplying the test fluid to the injector are changed for every injection-amount measuring unit. In this case, a frequency of the pressure pulsation, a pressure wave shape thereof and a pressure wave amplitude thereof are changed for every injection-amount measuring unit.
When the pressure pulsation of the test fluid injected by the injector is changed for every injection-amount measuring unit, the following trouble occurs. That is, even when a pulse current having the same pulse width and the same amplitude is applied to the coil of the same injector, and the test fluid having the same pressure is supplied, a measured result of the injection amount is changed for every injection-amount measuring unit. Further, when a measurement set value such as the pulse current and the test fluid pressure is changed, the measured injection amount using the changed measurement set value is sometimes changed for every injection-amount measuring unit.
Therefore, it is an object of the present invention to provide an injection-amount measuring unit for accurately measuring an injection amount of an injector in a relatively short period of time. It is another object of the present invention to provide an injection-amount measuring unit for measuring an injection amount which does not change for every injection-amount measuring unit.
In an injection-amount measuring unit according to an embodiment of the present invention, a passage area of a volume enlargement chamber is larger than a fluid inflow passage and a fluid outflow passage. Here, a fluid flows from a side of a fluid supply device into the volume enlargement chamber through the fluid inflow passage, and a fluid flows from the volume enlargement chamber to a side of a fuel injector (injector) through the fluid outflow passage. When a valve member of the injector performs intermittent fuel-injection, a pulsating pressure is generated in a fluid within the injector. When the pressure pulsation reaches the volume enlargement chamber from the fluid outflow passage, the pressure pulsation is reduced. That is, while a fluid is injected from the injector, fluctuating pressures of a fluid supplied to the injector can be reduced. Therefore, an injection amount can be accurately measured using a small number of injections, thereby performing a measuring operation in a small amount of time.
Here, multiple injection-amount measuring units are set, and a passage member changes in length and curvature for every injection-amount measuring device. Even in this case, when a pressure of a fluid supplied to the injector and a control current supplied to the electric driving member are set at the same values for every injection-amount measurement, injection-amount fluctuation of the injector is reduced for every injection-amount measuring unit. Accordingly, a degree of freedom of a set condition of the injection-amount measuring unit can be increased. In an injection-amount measuring unit according to an embodiment of the present invention, a feed distance of an adjusting pipe is adjusted so that a requested injection amount can be realized while the injection amount is measured. Accordingly, the injection amount of the injector can be adjusted in a small amount of time.
In an injection-amount measuring unit according to an embodiment of the present invention, the volume enlargement chamber is provided around a fuel inlet of the injector. Accordingly, the pressure pulsation generated in the fluid within the injector is immediately reduced. Here, multiple injection-amount measuring units are provided, and the passage member changes in length and curvature for every injection-amount measuring unit. Even in this case, when a pressure of a fluid supplied to the injector and a control current supplied to the electric driving member are set at the same values for every injection-amount measuring unit, injection-amount fluctuation of the injector can be further reduced for every injection-amount measuring unit.
In an injection-amount measuring unit according to an embodiment of the present invention, the fluid inflow passage and the fluid outflow passage are provided on lines different from each other, respectively. That is, the fluid inflow passage and the fluid outflow passage are not in the same line. Accordingly, the pressure pulsation can be effectively reduced in the volume enlargement chamber.
In an injection-amount measuring unit of an embodiment of the present invention, the fluid inflow passage and the fluid outflow passage are perpendicular to each other. Therefore, the pressure pulsation, transmitted from the injector into the volume enlargement chamber through the fluid outflow passage, experiences difficulty in transmitting the pulsation to the fluid inflow passage which is located to a side with respect to the fluid outflow passage. Accordingly, the pressure pulsation can be reduced in the volume enlargement chamber.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.